1. Field of the Invention
This invention relates to a vehicular seat apparatus having a mechanically strengthened reclining mechanism.
2. Description of the Prior Art
A seat apparatus for an automotive vehicle generally is equipped with a reclining mechanism for reclining a seat back in order provide a seated individual with maximum comfort. The reclining mechanism has an upper gear provided on the side of a seat-back frame, and a lower gear provided on the side of a seat-cushion frame. The number of teeth on one of these two gears is at least one less than the number of teeth on the other. The two gears are meshed with each other and supported on coaxial and eccentric shaft portions of a shaft. The reclining mechanism is so adapted that rotating the shaft makes it possible to recline the seat back relative to the seat cushion.
A seat belt is mandatory for the sake of passenger safety. As shown in FIG. 3, a seat apparatus 25 of the type in which a three-point seat belt 24 is incorporated in the seat includes a retractor 27 attached to a seat-back frame 26. When the vehicle sustains a collision or sudden stop, a very large rotational moment acts upon the reclining mechanism on the side of a side member of the seat-back frame 26 to which the retractor 27 is attached. The rotational moment is attributed to the weight of the belt acting upon an anchor bolt of a shoulder belt. As a consequence, a large load acts upon the portion where the upper and lower gears mesh, thereby causing deformation or breakage of the gear teeth or deformation of a release arm. In addition, a large load also acts upon a release arm and can cause deformation of the release arm.
In an effort to solve the aforementioned problem, the gears and release arm can be increased in wall thickness, and so can the related components. However, this expedient is undesirable as it merely increases the weight of the apparatus.